
One of Fleming's first thermionic diode valves, 1889
1889
1889
1889
1878
1918 - 2000
1915 - 1981
1873
1925; 1862
circa 1890
1877
1883 - 1905
1893 - 1965
1903 - 1990
1884
1917
1896-1897
1890
1895-1909
1880-1910
1896
1876-1884
1909-1914
1889
1886-1903
1892
1874
1834-1836
1880-1900
1910-1912
1880-1900
1880-1890
1900-1910
1871-1900
1899
circa 1891
1903
1910-1915
1903
1907 - 1993
1877 - 1963
1911 - 1980
1887-1888
1895 - 1971
1940-03
1880
circa 1893
circa 1893
circa 1893
circa 1893
1893
circa 1893